The present invention relates to cooling fans and in particular to a fan housing configured to reduce noise in a cooling fan.
The prior art for fans includes a housing and a fan assembly. The fan assembly fits into an air passage region provided in the housing. The fan assembly includes an impeller unit and a motor for driving the impeller unit. The housing typically comprises a base to which the motor is attached and an enclosure (or casing).
A common problem with fans is the noise they generate during operation. A particularly displeasing noise component is tonal noise. Tonal noise is a result of the rotation of the fan blades. The frequency spectrum of tonal noise comprises largely of components (fundamental and harmonics) of the blade passing frequency, which is the number of fan blades times the shaft speed (revolutions per second). Broadband noise is another noise component, but is less noticeable as compared to tonal noise since its frequency spectrum is generally much broader that the frequency spectrum of tonal noise and the amplitudes of its frequency components are lower.